GWT compilation fails: missing validation-api-1.0.0.GA-sources.jar when resolving from mavenLocal

[gallardo]

Our build failed during the :compileGwtJava task due to an unresolved dependency:

Execution failed for task ':compileGwtJava'.
> Could not resolve all files for configuration ':gwtCompileClasspath'.
   > Could not find validation-api-1.0.0.GA-sources.jar (javax.validation:validation-api:1.0.0.GA).
     Searched in the following locations:
         file:/var/lib/jenkins/.m2/repository/javax/validation/validation-api/1.0.0.GA/validation-api-1.0.0.GA-sources.jar

(The dependency was correctly resolved and downloaded)

Root Cause

Gradle was configured to use mavenLocal() as the first repository. When resolving dependencies, Gradle found the binary JAR for javax.validation:validation-api:1.0.0.GA in the local Maven repository (~/.m2), but that repository did not contain the corresponding *-sources.jar.
Because mavenLocal() had higher priority than remote repositories, Gradle did not continue searching elsewhere, resulting in a missing artifact during the GWT compilation phase.

> # The jar artifact is in maven local repository but not *-sources isn't:
> find /var/lib/jenkins/.m2/repository/javax/validation/validation-api/1.0.0.GA/ -name "*.jar"
/var/lib/jenkins/.m2/repository/javax/validation/validation-api/1.0.0.GA/validation-api-1.0.0.GA.jar
>
> # The both artifacts are available for gradle:
> find /var/lib/jenkins/.gradle/caches/modules-2/files-2.1/javax.validation/validation-api/1.0.0.GA/ -name "*.jar"
/var/lib/jenkins/.gradle/caches/modules-2/files-2.1/javax.validation/validation-api/1.0.0.GA/b6bd7f9d78f6fdaa3c37dae18a4bd298915f328e/validation-api-1.0.0.GA.jar
/var/lib/jenkins/.gradle/caches/modules-2/files-2.1/javax.validation/validation-api/1.0.0.GA/7a561191db2203550fbfa40d534d4997624cd369/validation-api-1.0.0.GA-sources.jar